The rotator cuff is a cuff-like tendon complex formed by the tendons of the supraspinatus, infraspinatus, teres minor and subscapularis muscles wrapped around the humeral head in the anterior, superior and posterior directions, which can affect the internal and external rotation and overhead movement of the shoulder joint and plays an extremely important role in maintaining the stability and movement of the shoulder joint. Rotator cuff injuries are more prevalent in middle-aged and elderly people, and their incidence increases significantly with age. They often have unbearable nocturnal pain and dysfunctional inability to raise the hand over the shoulder, which seriously affects the patient’s quality of life. The clinical presentation of this disease is similar to that of adhesive capsulitis, with shoulder pain and functional limitation, and is often mistakenly treated as frozen shoulder, with poor outcomes. Relying on history, clinical symptoms, and physical examination alone is not sufficient to differentiate frozen shoulder from rotator cuff injury. Arthroscopy is the gold standard for clinical diagnosis of rotator cuff injury, but it is not easily accepted by patients because it is an invasive test. MRI is by far the most ideal non-invasive method for examining rotator cuff injuries.